/* ============================================================
   EduProd KCET Physics — v4.0
   Font: Inter | Palette: Navy + Orange
   ============================================================ */

/* ── Variables ── */
:root {
  --bg:           #f4f7fb;
  --surface:      #ffffff;
  --text:         #0f1f3d;
  --muted:        #5a6e8a;
  --border:       #dde5f0;
  --shadow-sm:    0 2px 8px rgba(15,31,61,.06);
  --shadow:       0 6px 24px rgba(15,31,61,.10);
  --shadow-lg:    0 16px 48px rgba(15,31,61,.14);

  --primary:      #1a3a8f;   /* deep navy blue */
  --primary-dk:   #0e2460;
  --primary-lt:   #e8f0ff;
  --accent:       #f47c20;   /* energetic orange */
  --accent-dk:    #d96510;
  --accent-lt:    #fff0e4;
  --success:      #10a952;
  --success-lt:   #e6f8ed;
  --warning:      #f59e0b;
  --warning-lt:   #fef3c7;
  --danger:       #e03e3e;

  --radius-sm:    10px;
  --radius:       16px;
  --radius-lg:    24px;
  --radius-xl:    32px;
}

/* ── Reset ── */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

/* ── Base ── */
html { scroll-behavior: smooth; }
body {
  font-family: 'Inter', 'Segoe UI', system-ui, sans-serif;
  background: var(--bg);
  color: var(--text);
  font-size: 15px;
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

/* ── Typography ── */
h1 { font-size: clamp(1.9rem, 4vw, 3rem); font-weight: 900; line-height: 1.1; color: var(--primary); }
h2 { font-size: clamp(1.25rem, 2.5vw, 1.6rem); font-weight: 800; color: var(--primary); margin-top: 28px; margin-bottom: 10px; }
h3 { font-size: 1.05rem; font-weight: 700; color: var(--primary-dk); margin-bottom: 8px; }
p  { color: var(--muted); line-height: 1.75; }
a  { color: var(--primary); text-decoration: none; }
a:hover { color: var(--accent); }

/* ── Header ── */
.site-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 5%;
  height: 72px;
  background: var(--surface);
  border-bottom: 1px solid var(--border);
  position: sticky; top: 0; z-index: 100;
  box-shadow: var(--shadow-sm);
}

.brand img { height: 48px; width: auto; display: block; }

.site-nav { display: flex; align-items: center; gap: 4px; }
.nav-link {
  padding: 7px 14px; border-radius: var(--radius-sm);
  font-size: .875rem; font-weight: 600; color: var(--muted);
  transition: background .15s, color .15s;
}
.nav-link:hover { background: var(--primary-lt); color: var(--primary); }
.nav-link.active { background: var(--primary-lt); color: var(--primary); font-weight: 700; }

.nav-toggle {
  display: none; flex-direction: column; gap: 5px;
  background: none; border: none; cursor: pointer; padding: 6px;
}
.nav-toggle span { display: block; width: 22px; height: 2px; background: var(--text); border-radius: 2px; }

/* ── Main ── */
.site-main { width: min(1140px, 92%); margin: 0 auto; padding: 40px 0 64px; }

/* ── Footer ── */
.site-footer {
  background: var(--primary-dk);
  color: rgba(255,255,255,.65);
  padding: 28px 5%;
  margin-top: 60px;
}
.footer-inner { max-width: 1140px; margin: 0 auto; display: flex; align-items: center; justify-content: space-between; flex-wrap: wrap; gap: 12px; }
.footer-brand { font-size: .875rem; display: flex; align-items: center; gap: 10px; }
.footer-brand strong { color: #fff; }
.footer-tag { background: rgba(255,255,255,.1); padding: 3px 10px; border-radius: 20px; font-size: .75rem; }
.footer-links { display: flex; gap: 18px; }
.footer-links a { font-size: .82rem; color: rgba(255,255,255,.55); transition: color .15s; }
.footer-links a:hover { color: #fff; }
.footer-note { font-size: .78rem; }

/* ── Buttons ── */
.btn, .button {
  display: inline-flex; align-items: center; gap: 6px;
  padding: 10px 22px; border-radius: 40px;
  font-size: .875rem; font-weight: 700;
  border: 2px solid transparent; cursor: pointer;
  transition: all .18s ease; text-decoration: none;
  white-space: nowrap;
}
.btn:hover, .button:hover { transform: translateY(-2px); }

.btn-primary, .button.primary {
  background: var(--primary); color: #fff; border-color: var(--primary);
}
.btn-primary:hover, .button.primary:hover {
  background: var(--primary-dk); border-color: var(--primary-dk);
  box-shadow: 0 6px 20px rgba(26,58,143,.3); color: #fff;
}

.btn-accent {
  background: var(--accent); color: #fff; border-color: var(--accent);
}
.btn-accent:hover {
  background: var(--accent-dk); border-color: var(--accent-dk);
  box-shadow: 0 6px 20px rgba(244,124,32,.35); color: #fff;
}

.button {
  background: var(--surface); color: var(--primary);
  border-color: var(--border);
}
.button:hover {
  background: var(--primary-lt); border-color: var(--primary);
  color: var(--primary);
}

.btn-sm, .button.sm { padding: 7px 16px; font-size: .8rem; }

/* ── Pills / Badges ── */
.pill, .status {
  display: inline-block; padding: 5px 14px;
  background: var(--primary-lt); color: var(--primary);
  border-radius: 40px; font-size: .78rem; font-weight: 800;
  letter-spacing: .03em;
}
.pill-accent { background: var(--accent-lt); color: var(--accent-dk); }
.pill-success { background: var(--success-lt); color: var(--success); }

/* ── Cards ── */
.card {
  background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius); box-shadow: var(--shadow-sm);
  padding: 24px;
}
.card-hover { transition: transform .2s, box-shadow .2s; }
.card-hover:hover { transform: translateY(-4px); box-shadow: var(--shadow); }

/* ── Breadcrumb ── */
.breadcrumb {
  display: flex; align-items: center; gap: 6px;
  font-size: .8rem; font-weight: 600; color: var(--muted);
  margin-bottom: 10px; flex-wrap: wrap;
}
.breadcrumb a { color: var(--primary); }
.breadcrumb a:hover { color: var(--accent); }
.breadcrumb .sep { color: var(--border); }

/* ── Page actions bar ── */
.page-actions-bar {
  display: flex; gap: 8px; flex-wrap: wrap;
  margin-bottom: 24px;
}

/* ── Hero — home ── */
.hero-modern {
  display: grid;
  grid-template-columns: 1fr .85fr;
  gap: 40px;
  align-items: center;
  background: linear-gradient(135deg, #e8f0ff 0%, #f4f7fb 60%, #fff0e4 100%);
  border-radius: var(--radius-xl);
  padding: 52px 48px;
  border: 1px solid var(--border);
  box-shadow: var(--shadow);
  margin-bottom: 52px;
}
.hero-modern h1 { margin: 10px 0 18px; }
.hero-modern p  { font-size: 1.05rem; max-width: 560px; }
.badge-glow {
  display: inline-block; padding: 5px 14px;
  background: var(--primary); color: #fff;
  border-radius: 40px; font-size: .78rem; font-weight: 800;
  letter-spacing: .04em; margin-bottom: 14px;
}
.accent-text { color: var(--accent); }
.hero-buttons { display: flex; gap: 12px; flex-wrap: wrap; margin-top: 22px; }

/* Physics formula card (hero visual) */
.physics-formula-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 26px;
  box-shadow: var(--shadow-lg);
  position: relative; overflow: hidden;
}
.physics-formula-card::before {
  content: ""; position: absolute; right: -40px; top: -40px;
  width: 120px; height: 120px;
  background: rgba(244,124,32,.12); border-radius: 50%;
}
.formula-card-label {
  display: inline-block; background: var(--primary-lt); color: var(--primary);
  padding: 5px 12px; border-radius: 40px; font-weight: 800; font-size: .78rem;
  margin-bottom: 14px;
}
.formula-row {
  display: flex; justify-content: space-between; align-items: center;
  gap: 12px; padding: 13px 0; border-bottom: 1px solid var(--border);
}
.formula-row:last-of-type { border-bottom: none; }
.formula-row span { color: var(--muted); font-weight: 600; font-size: .875rem; }
.formula-row strong { color: var(--primary-dk); font-size: 1.15rem; }
.formula-note {
  margin-top: 14px; background: var(--accent-lt); color: #8a4104;
  border-radius: var(--radius-sm); padding: 12px 14px;
  line-height: 1.5; font-weight: 600; font-size: .875rem;
}

/* ── Method grid (home) ── */
.method-grid {
  display: grid;
  grid-template-columns: repeat(5, 1fr);
  gap: 14px; margin-bottom: 48px;
}
.method-card {
  background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 22px 16px;
  text-align: center; transition: all .2s;
}
.method-card:hover { transform: translateY(-5px); box-shadow: var(--shadow); border-color: var(--primary); }
.method-card h3 { font-size: .95rem; margin: 10px 0 6px; }
.method-card p  { font-size: .8rem; }
.step-num {
  width: 44px; height: 44px;
  background: var(--primary); color: #fff;
  font-weight: 900; font-size: 1.25rem;
  display: inline-flex; align-items: center; justify-content: center;
  border-radius: 50%; margin-bottom: 12px;
}

/* ── Subject cards ── */
.subject-cards {
  display: grid; grid-template-columns: repeat(auto-fit, minmax(220px,1fr));
  gap: 20px; margin: 20px 0 36px;
}
.subject-card {
  background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius-lg); padding: 28px 22px;
  text-align: center; box-shadow: var(--shadow-sm);
  transition: all .2s;
}
.subject-card.active { border-top: 4px solid var(--primary); }
.subject-card.disabled { opacity: .65; }
.subject-card:not(.disabled):hover { transform: translateY(-4px); box-shadow: var(--shadow); }
.subject-icon { font-size: 2.8rem; margin-bottom: 12px; }
.coming-soon-badge {
  display: inline-block; background: #eef1f8; color: #6b7a99;
  border-radius: 40px; padding: 5px 12px; font-size: .72rem; font-weight: 700;
  margin-top: 10px;
}

/* ── Continue card ── */
.continue-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-left: 5px solid var(--accent);
  border-radius: var(--radius-lg);
  padding: 30px 28px;
  display: flex; justify-content: space-between;
  align-items: center; gap: 20px;
  box-shadow: var(--shadow-sm);
}

/* ── Section heading ── */
.section-heading { margin: 36px 0 18px; }
.section-heading h2 { margin-top: 0; margin-bottom: 6px; }
.section-heading p { margin: 0; }

/* ── Chapter page ── */
.chapter-hero {
  background: linear-gradient(135deg, var(--primary) 0%, #0e2460 100%);
  border-radius: var(--radius-xl);
  padding: 40px 44px;
  color: #fff;
  margin-bottom: 32px;
  position: relative;
  overflow: hidden;
}
.chapter-hero::after {
  content: ""; position: absolute; right: -60px; top: -60px;
  width: 240px; height: 240px;
  background: rgba(255,255,255,.05); border-radius: 50%;
}
.chapter-hero .pill { background: rgba(255,255,255,.18); color: #fff; }
.chapter-hero h1 { color: #fff; margin: 12px 0 10px; font-size: clamp(1.6rem,3.5vw,2.4rem); }
.chapter-hero p  { color: rgba(255,255,255,.8); max-width: 660px; margin-bottom: 0; }

/* Chapter stats row */
.chapter-stats {
  display: flex; gap: 10px; flex-wrap: wrap;
  margin-top: 22px;
}
.stat-chip {
  background: rgba(255,255,255,.15);
  border: 1px solid rgba(255,255,255,.2);
  border-radius: var(--radius-sm);
  padding: 10px 18px;
  text-align: center; cursor: pointer;
  transition: background .2s;
  text-decoration: none; color: #fff;
}
.stat-chip:hover { background: rgba(255,255,255,.28); color: #fff; }
.stat-chip strong { display: block; font-size: 1.6rem; font-weight: 900; line-height: 1; }
.stat-chip span   { font-size: .72rem; font-weight: 600; opacity: .85; }

/* ── Learning path ── */
.learning-path {
  margin-bottom: 36px;
}
.learning-path-title {
  font-size: .72rem; font-weight: 800; text-transform: uppercase;
  letter-spacing: .08em; color: var(--muted); margin-bottom: 14px;
}
.path-steps {
  display: grid; grid-template-columns: repeat(5, 1fr); gap: 12px;
}
.path-step {
  background: var(--surface); border: 1.5px solid var(--border);
  border-radius: var(--radius); padding: 18px 14px;
  text-align: center; position: relative;
  transition: all .2s; text-decoration: none; color: var(--text);
  display: block;
}
.path-step::after {
  content: "→"; position: absolute; right: -10px; top: 50%;
  transform: translateY(-50%); font-size: 1rem; color: var(--border);
  font-weight: 700; z-index: 1;
}
.path-step:last-child::after { display: none; }
.path-step:hover {
  border-color: var(--primary); background: var(--primary-lt);
  transform: translateY(-4px); box-shadow: var(--shadow);
}
.path-step:hover .step-icon { background: var(--primary); color: #fff; }
.path-step .step-num-badge {
  font-size: .65rem; font-weight: 800; text-transform: uppercase;
  letter-spacing: .06em; color: var(--muted); margin-bottom: 8px;
}
.path-step .step-icon {
  width: 44px; height: 44px; border-radius: 50%;
  background: var(--primary-lt); color: var(--primary);
  display: inline-flex; align-items: center; justify-content: center;
  font-size: 1.3rem; margin-bottom: 10px;
  transition: background .2s, color .2s;
}
.path-step .step-title { font-size: .9rem; font-weight: 800; color: var(--primary-dk); margin-bottom: 4px; }
.path-step .step-desc  { font-size: .72rem; color: var(--muted); line-height: 1.4; margin-bottom: 8px; }
.path-step .step-time  { font-size: .68rem; font-weight: 700; color: var(--accent); }

/* Start here highlight */
.path-step.start-here {
  border-color: var(--accent); background: var(--accent-lt);
}
.path-step.start-here .step-icon { background: var(--accent); color: #fff; }
.path-step.start-here .step-title { color: var(--accent-dk); }
.path-step.start-here::before {
  content: "Start Here";
  position: absolute; top: -10px; left: 50%; transform: translateX(-50%);
  background: var(--accent); color: #fff;
  font-size: .62rem; font-weight: 900; letter-spacing: .05em;
  padding: 2px 10px; border-radius: 20px; white-space: nowrap;
}

/* ── Simulation section ── */
.sim-section {
  background: #0d1117;
  border-radius: var(--radius-xl);
  overflow: hidden;
  margin-bottom: 36px;
  border: 1px solid #30363d;
}
.sim-header {
  display: flex; align-items: center; justify-content: space-between;
  padding: 16px 22px; background: #161b22; border-bottom: 1px solid #30363d;
  flex-wrap: wrap; gap: 10px;
}
.sim-header-left { display: flex; align-items: center; gap: 10px; }
.sim-dot { width: 8px; height: 8px; border-radius: 50%; }
.sim-dot.red    { background: #ff5f57; }
.sim-dot.yellow { background: #febc2e; }
.sim-dot.green  { background: #28c840; }
.sim-title { color: #e6edf3; font-size: .9rem; font-weight: 700; }
.sim-badge { background: rgba(244,124,32,.2); color: #f47c20; padding: 3px 10px; border-radius: 20px; font-size: .72rem; font-weight: 700; }

.sim-tabs-bar {
  display: flex; gap: 8px; padding: 12px 22px;
  background: #161b22; border-bottom: 1px solid #30363d; flex-wrap: wrap;
}
.sim-tab {
  padding: 6px 16px; border-radius: 20px; font-size: .78rem; font-weight: 700;
  border: 1px solid #30363d; background: transparent; color: #8b949e;
  cursor: pointer; transition: all .15s;
}
.sim-tab:hover   { border-color: #f47c20; color: #f47c20; }
.sim-tab.active  { background: #f47c20; color: #fff; border-color: #f47c20; }

.sim-iframe-wrap { position: relative; }
.sim-iframe {
  display: block; width: 100%; border: none;
  min-height: 520px; background: #0d1117;
}
.sim-iframe.hidden { display: none; }

.sim-footer {
  padding: 12px 22px; background: #161b22; border-top: 1px solid #30363d;
  font-size: .78rem; color: #8b949e; display: flex; gap: 8px; align-items: center; flex-wrap: wrap;
}
.sim-footer strong { color: #e6edf3; }

/* ── Two-column chapter layout ── */
.chapter-body {
  display: grid; grid-template-columns: minmax(0,1fr) 320px;
  gap: 28px; align-items: start;
}

/* ── Content cards ── */
.content-card, .formula-card, .feature-card, .download-card {
  background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 22px;
  box-shadow: var(--shadow-sm);
}
.content-card.warning { background: var(--warning-lt); border-color: #e8c76a; }

/* Formula stack */
.formula-stack { display: grid; gap: 14px; }
.formula-card strong { font-size: .95rem; color: var(--primary-dk); display: block; margin-bottom: 8px; }
.formula-card code {
  display: block; background: var(--primary-lt); color: var(--primary);
  padding: 10px 12px; border-radius: var(--radius-sm);
  margin: 8px 0; font-weight: 700; font-size: .85rem;
}
.formula-card small { color: var(--muted); font-size: .8rem; line-height: 1.5; }
.formula-latex { background: #f8fafc; border: 1px solid var(--border); border-radius: var(--radius-sm); padding: 10px 12px; margin: 8px 0; overflow-x: auto; }

/* Formula guidance */
.formula-guidance-grid { display: grid; grid-template-columns: repeat(auto-fit,minmax(230px,1fr)); gap: 16px; }
.formula-use-card {
  background: var(--surface); border: 1px solid var(--border);
  border-left: 4px solid var(--primary); border-radius: var(--radius); padding: 18px;
}
.formula-use-card p { margin: 8px 0 0; font-size: .875rem; line-height: 1.6; }

.clean-list { padding-left: 20px; }
.clean-list li { margin-bottom: 8px; color: var(--muted); line-height: 1.65; }

/* ── Practice / Coach layout ── */
.practice-app, .coach-app {
  display: grid; grid-template-columns: minmax(0,1fr) 320px;
  gap: 22px;
}
.question-panel, .nudge-panel {
  background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius-lg); padding: 26px; box-shadow: var(--shadow-sm);
}
.nudge-panel {
  border-left: 4px solid var(--accent); background: #fffaf5;
}
.nudge-panel h3 { color: var(--accent-dk); }
@media(min-width:900px){
  .question-panel { position: sticky; top: 90px; align-self: start; }
}

.question-meta { display: flex; justify-content: space-between; gap: 12px; color: var(--muted); font-weight: 700; font-size: .85rem; margin-bottom: 16px; }
.options { display: grid; gap: 10px; margin-top: 18px; }
.option {
  border: 1.5px solid var(--border); background: #f8fafc;
  border-radius: var(--radius); padding: 13px 16px; cursor: pointer;
  transition: all .15s; font-size: .9rem; line-height: 1.5;
}
.option:hover { border-color: var(--accent); background: var(--accent-lt); transform: translateX(3px); }
.option.selected { border-color: var(--primary); background: var(--primary-lt); }

.practice-actions { display: flex; gap: 10px; flex-wrap: wrap; margin-top: 20px; }

.nudge-box, .feedback-box {
  min-height: 80px; border: 2px dashed var(--border);
  border-radius: var(--radius); padding: 14px; color: var(--muted);
  line-height: 1.65; margin-top: 12px; background: #fff;
}
.feedback-box.correct { color: var(--success); border-color: var(--success); background: var(--success-lt); }
.feedback-box.wrong   { color: #a84805; border-color: #e59d4b; background: var(--accent-lt); }

/* Check / Next buttons */
#btn-check, #sd-check {
  background: var(--accent); border-color: var(--accent); color: #fff;
}
#btn-check:hover, #sd-check:hover {
  background: var(--accent-dk); border-color: var(--accent-dk);
}

/* ── Progress bar ── */
.progress-tracker { height: 6px; background: var(--border); border-radius: 6px; margin-bottom: 28px; overflow: hidden; }
.progress-fill    { height: 100%; background: var(--accent); border-radius: 6px; width: 0%; transition: width .3s ease; }

/* ── Progress badge (localStorage) ── */
.progress-badge {
  display: inline-flex; align-items: center; gap: 8px;
  background: var(--success-lt); border: 1px solid #a7f3d0;
  border-radius: var(--radius); padding: 10px 16px;
  font-size: .82rem; font-weight: 600; color: var(--success);
  margin-bottom: 20px;
}
.progress-badge .pb-icon { font-size: 1.1rem; }

/* ── Timer ── */
.timer-display {
  font-family: 'Courier New', monospace;
  font-size: 1rem; font-weight: 900;
  background: var(--primary-dk); color: #ffd966;
  padding: 5px 14px; border-radius: 20px;
}

/* ── Speed Drill / Dynamic Drill ── */
.dynamic-layout { display: grid; grid-template-columns: 300px minmax(0,1fr); gap: 22px; }
.pattern-panel, .sim-controls, .sim-canvas-card {
  background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius-lg); box-shadow: var(--shadow-sm); padding: 24px;
}
.pattern-list { display: grid; gap: 10px; }
.pattern-card {
  border: 1.5px solid var(--border); background: #f8fafc;
  border-radius: var(--radius); padding: 14px; cursor: pointer; transition: all .15s;
}
.pattern-card:hover, .pattern-card.active { border-color: var(--accent); background: var(--accent-lt); }
.pattern-card strong { display: block; color: var(--primary-dk); margin-bottom: 4px; font-size: .875rem; }
.pattern-card small  { display: block; color: var(--muted); font-size: .78rem; line-height: 1.5; }

/* Inline simulation (graphs chapter) */
.sim-layout { display: grid; grid-template-columns: 300px minmax(0,1fr); gap: 22px; }
.slider-label { display: flex; justify-content: space-between; gap: 12px; margin-top: 16px; color: var(--muted); font-weight: 700; font-size: .875rem; }
.slider-label strong { color: var(--primary); }
.sim-controls input[type=range] { width: 100%; margin-top: 8px; accent-color: var(--primary); }
.sim-stats { display: grid; gap: 8px; margin-top: 20px; }
.sim-stats div { background: #f8fafc; border: 1px solid var(--border); border-radius: var(--radius-sm); padding: 10px 14px; display: flex; justify-content: space-between; }
.sim-stats span { color: var(--muted); font-weight: 600; font-size: .85rem; }
.sim-stats strong { color: var(--primary); font-weight: 800; }
.sim-tabs { display: flex; gap: 8px; flex-wrap: wrap; margin-bottom: 12px; }
#motion-canvas { width: 100%; max-width: 100%; background: #fff; border: 1px solid var(--border); border-radius: var(--radius); }
.sim-note { margin-top: 10px; background: var(--primary-lt); border-radius: var(--radius-sm); padding: 12px 14px; color: var(--primary); font-weight: 700; font-size: .875rem; line-height: 1.5; }

/* ── Mini test / Chapter Check ── */
.test-toolbar {
  display: flex; justify-content: space-between; align-items: center;
  background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius-lg); padding: 14px 20px;
  box-shadow: var(--shadow-sm); margin-bottom: 20px; font-weight: 700;
}
.test-question {
  background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius-lg); padding: 22px; margin-bottom: 14px;
  box-shadow: var(--shadow-sm);
}
.bottom-submit-bar {
  display: flex; justify-content: center;
  margin: 28px 0 12px; padding: 18px;
  background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius-lg); box-shadow: var(--shadow-sm);
}
.submit-large { min-width: 240px; text-align: center; font-size: 1rem; padding: 14px 28px !important; }

/* Result + analytics */
.result-card { display: none; padding: 24px; margin-top: 20px; }
.result-card.show { display: block; }
.explanation { margin-top: 10px; padding: 12px; background: #f7fbff; border-radius: var(--radius-sm); color: var(--muted); line-height: 1.65; }
.analytics-grid { display: grid; grid-template-columns: repeat(auto-fit,minmax(200px,1fr)); gap: 14px; margin-top: 16px; }
.analytics-card { background: #f8fafc; border: 1px solid var(--border); border-left: 4px solid var(--primary); border-radius: var(--radius); padding: 16px; }
.analytics-card.weak { border-left-color: var(--accent); background: var(--accent-lt); }
.analytics-card strong { display: block; color: var(--primary); font-size: 1.5rem; margin-top: 6px; }
.recommendation-box { background: var(--accent-lt); color: #8a4104; border-radius: var(--radius); padding: 16px; margin-top: 16px; line-height: 1.65; }

/* ── Coach ── */
.step-list { min-height: 160px; }
.coach-block { background: #f8fafc; border: 1px solid var(--border); border-radius: var(--radius); padding: 16px; margin-top: 14px; }
.step-item { background: var(--primary-lt); border-radius: var(--radius-sm); padding: 10px 12px; margin-bottom: 8px; font-size: .875rem; }
.target-box { display: inline-block; margin: 14px 0; padding: 7px 14px; border-radius: 40px; background: var(--accent-lt); color: var(--accent-dk); font-weight: 800; font-size: .875rem; }
.pyqp-badge { display: inline-block; background: var(--accent-lt); color: var(--accent-dk); border-radius: 40px; padding: 4px 10px; font-size: .75rem; font-weight: 800; margin-left: 6px; }

/* ── Downloads ── */
.download-section { margin-top: 28px; }
.download-grid { display: grid; grid-template-columns: repeat(auto-fit,minmax(240px,1fr)); gap: 16px; }
.download-card { border-left: 4px solid var(--primary); }
.download-card h3 { margin-top: 0; }

/* ── Unit list ── */
.unit-list { display: grid; gap: 14px; }
.unit-card {
  background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius-lg); padding: 20px 24px;
  display: flex; justify-content: space-between; gap: 16px; align-items: center;
  box-shadow: var(--shadow-sm); transition: all .2s;
}
.unit-card:hover { transform: translateX(4px); border-color: var(--primary); }
.planned-badge { display: inline-block; background: #f3f5f9; color: var(--muted); border-radius: 40px; padding: 5px 12px; font-size: .78rem; font-weight: 700; }

/* ── Mode grid (physics page) ── */
.mode-grid { display: grid; grid-template-columns: repeat(auto-fit,minmax(200px,1fr)); gap: 18px; margin-top: 24px; }
.mode-card { background: var(--surface); border: 1px solid var(--border); border-top: 3px solid var(--accent); border-radius: var(--radius); padding: 22px; box-shadow: var(--shadow-sm); }

/* ── Grid helpers ── */
.grid-section { display: grid; grid-template-columns: repeat(auto-fit,minmax(220px,1fr)); gap: 18px; margin-top: 22px; }
.two-column   { display: grid; grid-template-columns: minmax(0,1fr) 320px; gap: 24px; }
.chapter-list { display: grid; grid-template-columns: repeat(auto-fit,minmax(220px,1fr)); gap: 18px; margin-top: 22px; }
.chapter-card { background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius); padding: 22px; box-shadow: var(--shadow-sm); transition: all .2s; }
.chapter-card:hover { transform: translateY(-4px); box-shadow: var(--shadow); }

/* ── Page heading ── */
.page-heading { margin-bottom: 26px; }
.page-heading h1 { margin-top: 8px; }

/* ── Teacher note ── */
.teacher-ready-note { background: var(--accent-lt); color: #8a4104; border-radius: var(--radius); padding: 14px 16px; font-weight: 700; line-height: 1.55; }

/* ── Responsive ── */
@media(max-width:900px){
  .site-nav { display: none; flex-direction: column; position: absolute; top: 72px; left: 0; right: 0; background: var(--surface); padding: 12px; border-bottom: 1px solid var(--border); box-shadow: var(--shadow); z-index: 99; }
  .site-nav.open { display: flex; }
  .nav-toggle { display: flex; }
  .hero-modern { grid-template-columns: 1fr; padding: 36px 28px; border-radius: var(--radius-xl); text-align: center; }
  .hero-buttons { justify-content: center; }
  .method-grid { grid-template-columns: repeat(auto-fit,minmax(140px,1fr)); }
  .path-steps { grid-template-columns: 1fr 1fr; }
  .path-step::after { display: none; }
  .path-step.start-here { grid-column: span 2; }
  .chapter-body, .two-column { grid-template-columns: 1fr; }
  .practice-app, .coach-app { grid-template-columns: 1fr; }
  .dynamic-layout, .sim-layout { grid-template-columns: 1fr; }
  .unit-card { flex-direction: column; align-items: flex-start; }
  .continue-card { flex-direction: column; align-items: flex-start; }
}
@media(max-width:600px){
  .path-steps { grid-template-columns: 1fr; }
  .path-step.start-here { grid-column: span 1; }
  .chapter-stats { flex-direction: column; }
  .stat-chip { text-align: left; }
  .site-main { padding: 24px 0 48px; }
}


/* v4.1 production positioning: differentiators */
.differentiator-section{
  margin: 44px 0 34px;
}
.section-heading.compact{
  margin-bottom: 18px;
}
.section-heading.compact h2{
  margin-bottom: 6px;
}
.differentiator-grid{
  display:grid;
  grid-template-columns:repeat(auto-fit,minmax(250px,1fr));
  gap:20px;
}
.differentiator-card{
  background:#fff;
  border:1px solid var(--border);
  border-radius:28px;
  padding:26px;
  box-shadow:var(--shadow);
  position:relative;
  overflow:hidden;
}
.differentiator-card::before{
  content:"";
  position:absolute;
  top:0;
  left:0;
  right:0;
  height:5px;
  background:linear-gradient(90deg,var(--primary),var(--accent));
}
.diff-icon{
  font-size:2.2rem;
  margin-bottom:12px;
}
.differentiator-card h3{
  color:var(--primary-dark);
  margin:0 0 10px;
}
.differentiator-card p{
  color:var(--muted);
  line-height:1.6;
  margin:0;
}


/* v4.2 simulation container sizing fix */
.sim-section{
  max-width: min(1380px, 96vw);
  margin-left: auto;
  margin-right: auto;
}
.sim-iframe-wrap{
  height: clamp(720px, 82vh, 920px);
  overflow: hidden;
}
.sim-iframe{
  width: 100%;
  height: 100%;
  min-height: 720px;
  overflow: hidden;
}
@media(max-width:900px){
  .sim-section{
    max-width: 100%;
    border-radius: 22px;
  }
  .sim-iframe-wrap{
    height: 760px;
  }
  .sim-iframe{
    min-height: 760px;
  }
}


/* v4.3 simulation fit fix: simulations scale inside iframe */
.sim-iframe-wrap{
  height: clamp(720px, 78vh, 860px);
  overflow: hidden !important;
}
.sim-iframe{
  width: 100%;
  height: 100%;
  min-height: 720px;
  overflow: hidden !important;
}